CPM Homework Help : APCALC Problem 8-21

Write an expression for the area of the shaded region at right. The outside circle has radius $R$ and the inside circle has radius $r$ .

Hint:

$\text{Area(large disk) }- \text{ Area(small disk)}$

2 concentric circles, with shaded region between circles, inner circle radius labeled, small letter, r, larger circle radius labeled, capital letter, R.